1. Field of the Invention
The present invention relates to glycopeptides and peptides which have a taste improving function, particularly a kokumi taste imparting function. The present invention more specifically relates to such glycopeptides and peptides per se, a method for imparting the kokumi taste to foods or seasonings with the use of such a glycopeptide(s) and/or the peptide(s), a method for improving foods in regard to kokumi taste by the use of a seasoning containing such a glycopeptide(s) and/or the peptide(s), and foods or seasonings to which the kokumi taste has been imparted by such a kokumi taste improving method.
2. Discussion of the Background
The term kokumi taste refers to a taste which cannot be expressed by the five basic tastes (sweet taste, salt taste, sour taste, bitter taste, and umami taste), and which is obtainable by enhancing not only the basic tastes but also tastes around, or peripheral to, the basic tastes, such as thickness, spread, continuity, unity, and the like. Heretofore, some methods for imparting a kokumi taste have been reported. Among them, there are known a method in which glutathione is added (see, Japanese Patent No. 1464928), a method in which a heated product of gelatin and tropomyosin is added (see, Japanese Patent Application Laid-open (Kokai) No. Hei 10-276709), a method in which a sulfone group-containing compound is added (see, Japanese Patent Application Laid-open (Kokai) No. Hei 8-289760), and the like.
Further, as a kokumi taste imparting method other than the methods described above, an attempt has been made to impart a kokumi taste by increasing the ratio occupied by peptides in a seasoning (see, “Food Processing and Ingredients”, vol 31, No. 12, pp. 17-20 (1996)). This is an attempt to increase the amount of peptides in the whole of a food to impart a kokumi taste to the whole of the food or foods containing the peptides. However, such an attempt failed to provide such a desired effect, because, for example, the titer was low and peptides with bitterness imparted a bitter taste. Further, as described in Japanese Patent Application Laid-open (Kokai) No. 2002-335904, an attempt has been made to provide a seasoning for imparting a kokumi taste obtained by binding sugar and an unspecified peptide according to the Maillard reaction. However, the effect of such seasoning was not so strong, and the seasoning often imparts a negative effect when added to foods, such as impartment of a bitter taste or coloring due to the browned product.
Thus, there remains a need for a method for imparting a kokumi taste to a food. There also remains a need for compounds and seasonings which are effective for imparting a kokumi taste to a food.